Shock absorber for drilling machines



April 5, 1955 w. w. WALKER SHOCK ABSORBER FOR DRILLING MACHINES 3 Sheets-Sheet 1 Filed Dec. 9, 1950 INVENTOR. William W Walker @enfl SHOCK ABSORBER FOR DRILLING MACHINES Filed Dec. 9. 1950 3 Sheets-Sheet 2 INVENTOR. William M Walker April 5, 1955 w. w. WALKER SHOCK ABSORBER FOR DRILLING MACHINES Filed Dec. 9, 1950 5 Sheets-Sheet 3 INVENTOR. William M! Wal United States Patent SHOCK ABSORBER FOR DRILLING MACHINES William W. Walker, Wichita Falls, Tex. Application December 9, 1950, Serial No. 200,031 Claims. (Cl. 255-16) This invention relates to improvements in shock absorber mechanism for cable drilling tools used with well drilling machines of the type known as spudders.

Various types of shock absorbers for well drilling machines have been proposed heretofore, but these have been complex in construction, difficult to repair and inadequate in absorbing the shock of the cable, and were short lived, due to the fatigue to which the parts were subjected.

The present invention is simple in construction, easy to install, replace or repair, and is effective in absorbing shock to the drilling machine caused by the cable lifting the heavy drilling tools, and will last over a long period of time.

An object of this invention is to provide a simple, effective shock absorber for a spudder drilling rig.

Another object of this invention is to provide a mechanism for dampening the shock to the spudding machine caused by the percussion method of drilling.

An embodiment of this invention is illustrated in the accompanying drawings, in which:

ig. 1 is a side elevational view of a spudder drilling rig on which the shock absorber mechanism is used;

Fig. 2 is anenlarged elevational view of the shock absorber assembly, showing the spudding sheave, and with parts brokenaway and shown in section to bring out the details of construction;

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2, looking in the direction indicated by the arrows; an

Fig. 4 is a perspective view of the shock absorber member removed from the drilling machine.

With more detailed reference to the drawing the numeral 1 generally designates a well drilling machine known as a spudder, which machine is usually mounted on wheels 2, and has a frame work 3 upon which is mounted an engine 4. A cable spooling drum 5, and a mast 6, uprig "ts 7 and spudding arms 8 are also provided on said spudder. The arms 8 are each made of a channel member, U-shaped in cross section to the open side of which is welded a plate 8.

A transverse shaft 9 is located across frame 3 and has a band wheel 10 mounted intermediate the ends thereof and secured thereto, which band wheel 10 is driven by engine 4 through belt 11. Cranks 12 are positioned, one on each outer end of the transverse shaft 9 and a pitman 13 is pivotally connected at its lower end to the respective cranks.

The upper end of each pitman 13 is pivotally connected to spudder arms 8, so upon rotation of band wheel 10 and cranks 12 a reciprocating movement will be transmitted by pitmans 13 to spudder arms 8 which will impart an arcuate motion to the spudder arms 8, as indicated in dot-dash outline in Fig. 1.

Drilling cable 14 is normally wound on a drilling drum 5 and passes over cable sheaves 15, 16 and 17 to suspend well drilling tools 18 therefrom. The cable sheave 16 is mounted on shaft 19 for rotary and longitudinal movement. The shaft 19 is mounted between a pair of arms 20, as will be seen in Figs. 2 and 3. The arms 20 extend downward and are secured to tubular shaft 21, as by welding at 22. The tubular shaft 21 is journaled on a shaft 23 and the shaft 23 is bindingly secured to spudder arms 8 by U-bolts 24. The tubular shaft 21 has a slight oscillating movement on the shaft 23 for reasons which will appear. The shaft 23 protrudes outward from spudder arms 8 and journals the upper ends of the respective pitmans 13 thereon. Inthis manner the shaft 23 is fixed against rotation and yet serves the dual purpose of connecting the pitmans to the respective spudding arms and supporting the shaft 21 to which the arms 20 are secured.

Two spaced transverse support members 26 are secured in a conventional manner to the arms 8 for supporting the shock absorber element 25.

The shock absorber element 25 comprises inner tubular shaft 21, two outer semi-cylindrical members 27 and 28. These semi-cylindrical members 27 and 28 have outturned flanges 29 and 30 respectively, extending therefrom. Ribs 31 are secured to the semi-cylindrical member 27 and to the out-turned flange 29 so as to provide braces within the length of the semi-cylindrical member 27. Holes 32 are formed in the out-turned flanges 29 and 30, so the holes in the respective flanges will register, and which holes are so arranged as to register with holes in transverse members 26 to enable bolts 33 to pass therethrough. Spaced intermediate the outer diameter of tubular shaft 21 and the inner diameter of semi-cylindrical members 27 and 28 is resilient material 34 having the characteristics of rubber or synthetic rubber. This resilient material is bonded to the outer diameter of tubular shaft 21 and to the inner diameter of semicylindrical members 27 and 28, which material is yieldable within the elastic and bond limits thereof.

Operation With the cable 14 passing off drum 5 and over sheave 15 and under sheave 16 and over sheave 17, and with the weighted tools 18 depending from the cable 14 when the mast 6 is in upright position, and with the arms 20 leaning in an angular position as indicated. in Figs. 1 and 3, a torsion is exerted by arms 20 upon tubular shaft 21 and since the tubular shaft 21 is also bonded to resilient element 34, torsion is applied to the resilient element and since the outer diameter of the resilient element is bonded to the inner diameter of the semi-cylindrical members 27, 28, a torsional reaction is set up on outer semi-cylindrical members 27-28 which are rigidly secured to transverse members 26. With the resilient member 34 in torsion in this manner, the degree of shock to the machine is controlled when a sudden jerk is applied to the line 14.

The angle at which the arms 20 are secured to the tubular shaft 21, as by welding, is a determining factor in how extensive the torque that is applied to the resilient element 34 is. When the arms 20 are mounted to extend outward approximately horizontally, a vertical pull on cable 14 will apply the greatest torque and consequently move the arms 20 and sheave 16 through the greatest arc, and also give the greatest dampening effect between the vertical upward pull on cable 14 and the arms 8. However, the elastic limits and bond limits of the resilient material can only be worked to a certain degree without the possibility of fracture. With the arms 20 in a vertical position (as shown in dotted lines in Fig. l) and with a vertical pull on the cable 14, the only dampening effect that the resilient element 34 will present is the compressibility of the resilient material.

However, by extensive tests, it has been found that the most desirable angle at which the arms 20 should protrude forward is approximately thirty degrees included angle from the vertical. It is found that the torsion on the shaft 21 will cause the yielding of arms 20 to within a few degrees of vertical, and as the arms work through this arcuate movement, the angle of the arms approaches the same angle as the pull, that is, in alignment with the cable 14, at which point there would be no increase in torsion. By having the arms attached in this manner, it will be readily appreciated that heavy drilling stems can be suspended from the cable and the shock thereof to the machine cushioned, and as the resilient material approaches the elastic and bonding limits, the arms become more nearly vertical, which relieves the resilient material of further torsional strain and apply merely a compressive strain to the resilient material 34 encased within the semi-cylindrical members 2728.

It is to be appreciated that the angle of the arms, the weight of the tools, the speed of the cable and the cylindrical thickness and the degree of resiliency of the material 34 are the four factors that have to be considered in the proper designing of the shock absorber, as herein set forth.

It has been found that the most suitable working range of the shock absorber arms is within the limits of twenty degrees to forty-five degrees of vertical.

With the spudder arms operating at 20 to 50 movements per minute and often lifting tools weighing up to 6000 pounds, considerable shock would be transmitted to the mechanism of the spudder and cause the fastenings to become loosened or to break and the equipment in general to become loosened. However, with the present invention, the tools will be lifted quickly and the resilient element 34 will respond in torsion to absorb the shock to the necessary degree to lift the tools, but not sufficient to cause a fracture or break in the resilient material over a long period of use.

it is to be pointed out that the cylindrical thickness of the material, that is the difference between the internal diameter and the external diameter of the resilient material also determines the amount of torsion that can be applied without fracture. The resiliency of the material and the manner in which the material has been processed all affect the results produced by the shock absorber. Therefore, if the inner tubular shaft 21 has an 8 outside diameter and the inner diameter of the semi-cylindrical members 27-28 is 12", a 2" thickness of resilient material will surround shaft 21 for the torque therefrom to react upon. However, if this thickness is increased to four inches, a greater arcuate movement is possible but with the same resiliency of material the arms 20 will withstand less torque. These, and the factors mentioned above are determined by the weight of the tools and the speed at which the spudder is operated.

l n the drilling of wells by the cable tool method, it is desirable to have the tools reach ahead and hit the bottom of the Well at each stroke, although the normal length of the cable and tools is slightly less than the depth of the well. This enables the stretch in the cable and the resiliency accorded by the shock absorber to lend suflicient yieldability to permit this action.

While the invention has been illustrated and described in one embodiment thereof, it is to be understood that changes may be made in the minor details of construction and adaptations made to different working conditions without departing from the spirit of the appended claims.

Having thus clearly shown and described the invention,

what is claimed as new and desired to secure by Letters Patent is:

1. A sheave mounting for a spudder drilling machine comprising pivotally mounted spudder arms, a frame mounted on and fixed to said spudder arms between the ends thereof, a cylindrical member fixed upon said frame, a tubular shaft extending through said cylindrical member, a resilient connection between said tubular shaft and said cylindrical member, a transverse shaft fixed to the outer ends of said spudder arms and extending through said tubular shaft, crank arms fixed to said tubular shaft, a load supporting sheave rotatably supported at the outer ends of said crank arms, the load on said sheave tending to rotate said tubular shaft to the limit of the yielding of said resilient connection.

2. The invention according to claim 1 in which said cylindrical member comprises two semi-cylindrical members having flanged edges and means for securing said edges together to form a single cylindrical member.

3. The invention according to claim 1 in which said resilient connection consists of rubber-like material bonded to the interior of said cylindrical member and to the exterior of said tubular shaft.

4. In a spudder machine a pair of spudder arms pivoted at one end and having a transverse shaft fixed to and connecting the other ends, a frame mounted on and fixed to said spudder arms, a cylindrical member fixedly secured upon said frame, a tubular shaft mounted on said transverse shaft and extending through said cylindrical member, a rubber-like material bonded to the interior of said cylindrical member and to the exterior of said tubular shaft, a pair of crank arms fixed to the tubular shaft, a sheave rotatably mounted between the outer ends of said crank arms and pitmans operatively connected to said spudder arms for oscillating them.

5. The invention according to claim 4 in which said cylindrical member comprises semi-cylindrical members having flanged edges bolted together.

References Cited in the file of this patent UNITED STATES PATENTS 1,617,668 Clark Feb. 15, 1927 2,003,255 Duff May 28, 1935 2,396,579 Krotz Mar. 12, 1946 2,477,187 Lanchner July 26, 1949 2,596,411 Jordon May 13, 1952 

